What is POST? (Power-On Self-Test)
POST is the quick hardware check a PC runs every time you press the power button, before Windows starts loading. It confirms that the CPU, RAM, graphics and storage are present and responding.
What a failed POST looks like
The fans spin and the lights come on, but the monitor stays black and Windows never appears. Technicians call this a “no POST”. Many motherboards show which stage failed with a row of small debug lights labelled CPU, DRAM, VGA and BOOT, or with a pattern of beeps.
Common causes
RAM that has worked loose, a graphics card that is not seated or powered properly, a failing PSU, or a motherboard fault. A PC that fails POST straight after being moved or cleaned usually has something unseated. One that fails after a power trip is more likely to have a power supply or motherboard problem.
What you can check yourself
Make sure the monitor cable is plugged into the graphics card and not the motherboard, reseat the RAM, and try one stick at a time. Our PC won’t turn on troubleshooting guide walks through the steps in order. If it still will not POST, the fault needs testing with known-good parts.